The synthesis, spectroscopic and electrochemical characterisation of Ru(II) polypyridyl complexes containing hydroquinone
Lynch, Fiona Catherine (2006) The synthesis, spectroscopic and electrochemical characterisation of Ru(II) polypyridyl complexes containing hydroquinone. PhD thesis, Dublin City University.
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A range of mononuclear and dinuclear [Ru(bpy)2L]+ and [Ru(bpy)2(L)Ru(bpy)2]2+ complexes where L is 3(2’,5,-dimethoxyphenyl)-5-(pyndm-2’’-yl)-lH-r,2’,4’-tnazole, 3 (2 \ 5 ’ -dimethoxyphenyl)-5-(pyrazin-2”-yl)-1H-1’ ,25,4 ’ -tnazole, l,4-bis(5’-(pyndin-2”- yl)-1H-1’ ,2 ’ ,4’ ,-tnazol-35 -yl)-2,5-dimethoxyphenyl, l,4-bis(5’-(pyrazin-2,,-yl)-lHr ,2 ,,4,r tnazol-3’-yl)-2,5-dimethoxyphenyl and their hydroquinone and qumone analogues are reported in this thesis. Chapter one is an introductory chapter, which provides relevant background information and assists in placing the ideas and data contained in the main body of this thesis in context, while chapter two denotes the methods and procedures employed during the synthesis and characterisation of the complexes presented in the subsequent chapters. In chapter three the first group of ruthenium (II) polypyndyl complexes are described. These complexes are characterised by the presence of tnazole moieties and a dimethoxyphenyl group. These dimethoxyphenyl compounds represent model complexes for examination of the ensuing hydroquinone and qumone complexes. Synthesis of the hydroquinone and qumone complexes was also achieved via these dimethoxyphenyl counterparts. Chapter four pertains to the synthesis and charactensation of the mononuclear and dinuclear hydroquinone complexes, which differ only from the dimethoxyphenyl complexes by the presence of a dihydroxyphenyl group. These complexes exhibit behaviour comparable in a number of ways to their dimethoxy analogues except for additional redox processes in the anodic region of their cyclic voltammograms. These dihydroxyphenyl complexes also display interesting spectroelectrochemical behaviour, which was not noted in the spectra of the protected analogues, and that hence may be indicative of proton transfer between the hydroquinone and tnazole moieties. The synthesis and charactensation of the qumone complexes, which contain qumone moieties in place of the dihydroxy groups, is descnbed in chapter five. There is no quenching of the excited state noted for these complexes. All of the compounds obtained have been charactensed using [HNMR, IR, UV/Vis and emission spectroscopies both at room and low temperatures and in neutral and acidic media. The acid-base properties of each of the complexes have also been investigated in aqueous solutions. The electronic structures of the mononuclear pyndine containing qumone and hydroquinone complexes have been examined using Gausssum and DOS spectra have hence been generated in order to ascertain the nature of the HOMO and LUMO levels. In the final chapter, chapter six, a comprehensive examination of the behaviour of the range of complexes is provided and a number of observations and conclusions are proffered along with suggestions for future work. Generally, the behaviour of each of the complexes was found to differ depending both on whether the complex contained a pyrazyl or a pyndyl group and on the nature of the pendant phenyl moiety Emission, lifetime, electrochemical and spectroelectrochemical analyses of the pyrazine containing complexes suggest that switching of the excited states of these complexes from the bipyndyl moiety to the ligand occurs upon protonation of the complex. Three appendices are also provided the first of which, appendix I, contains additional NMR data Appendix II contains in-depth electrochemical studies exploring solvent conditions and identifying the optimum working-electrode Finally, appendix III compnses of additional syntheses undertaken dunng these studies, which have not been included in the mam body of the thesis
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